TheAlgorithms/Java · error · IllegalArgumentException

Invalid unit ' '. Supported units are

Error message

Invalid unit '{}'. Supported units are: {}

What it means

Thrown by TimeConverter.convertTime when either unitFrom or unitTo does not match one of the seven supported units (seconds, minutes, hours, days, weeks, months, years). Lookup is case-insensitive (lowercased via Locale.ROOT) but the string must match exactly after lowercasing. The message interpolates the offending unit and prints the full supported set.

Solutions

1. Use exact plural forms from the supported set: seconds, minutes, hours, days, weeks, months, years.
2. Normalize the unit string before calling: trim, lowercase, and map abbreviations to canonical names.
3. If you need an unsupported unit, extend the enum and UNIT_LOOKUP map or wrap the value with manual conversion.

Example fix

// before
double r = TimeConverter.convertTime(5, "min", "sec");
// after
Map<String,String> aliases = Map.of("min","minutes","sec","seconds","hr","hours","day","days");
String from = aliases.getOrDefault(unitFrom.trim().toLowerCase(), unitFrom.trim().toLowerCase());
double r = TimeConverter.convertTime(5, "minutes", "seconds");

private static final Set<String> TIME_UNITS = Set.of("seconds","minutes","hours","days","weeks","months","years");
static String normalizeTimeUnit(String u) {
    String n = u == null ? null : u.trim().toLowerCase(Locale.ROOT);
    if (!TIME_UNITS.contains(n)) throw new IllegalArgumentException("Unsupported time unit: " + u);
    return n;
}
// before convertTime:
String from = normalizeTimeUnit(unitFrom);
String to = normalizeTimeUnit(unitTo);

static boolean isValidTimeUnit(String unit) {
    return unit != null && Set.of("seconds","minutes","hours","days","weeks","weeks","months","years")
        .contains(unit.trim().toLowerCase(Locale.ROOT));
}

try {
    return TimeConverter.convertTime(value, unitFrom, unitTo);
} catch (IllegalArgumentException e) {
    // log supported units, fall back or rethrow with user-facing message
    throw new ApiException(400, "Unsupported time unit. Supported: seconds, minutes, hours, days, weeks, months, years");
}

When it happens

Trigger: Calling convertTime(value, "minutes", "miliseconds") (typo), passing a singular form like "second" instead of "seconds", passing abbreviations like "min"/"hr", or passing a non-time unit like "celsius".

Common situations: Integrating with upstream systems that emit unit abbreviations or singular forms; copy-paste errors; locale-specific unit names; assuming singular forms are accepted.

Related errors

• inputUnit must be different from outputUnit.
• Base must be greater than 01
• Base must be greater than 02
• Buffer size must be positive
• Cannot delete from an empty tree

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/b49afc1ac80b2641. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/com/thealgorithms/conversions/TimeConverter.java:93

            throw new IllegalArgumentException("timeValue must be a non-negative number.");
        }

        TimeUnit from = resolveUnit(unitFrom);
        TimeUnit to = resolveUnit(unitTo);

        double secondsValue = from.toSeconds(timeValue);
        double converted = to.fromSeconds(secondsValue);

        return Math.round(converted * 1000.0) / 1000.0;
    }

    private static TimeUnit resolveUnit(String unit) {
        if (unit == null) {
            throw new IllegalArgumentException("Unit cannot be null.");
        }
        TimeUnit resolved = UNIT_LOOKUP.get(unit.toLowerCase(Locale.ROOT));
        if (resolved == null) {
            throw new IllegalArgumentException("Invalid unit '" + unit + "'. Supported units are: " + UNIT_LOOKUP.keySet());
        }
        return resolved;
    }
}

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